Grammar-Checking Software Is Soft on Grammar Errors

By Mark Nichol

You want to improve your grammar, but you’re disinclined to invest time and energy to laboriously study print or online resources about sentence construction. You’ve seen ads on the Internet about grammar checkers, and you decide to check them out. How useful is grammar-checking software?

After visiting five grammar-checker websites and using (the free versions of) their products, my conclusion is that software is no substitute for wetware (otherwise known as your brain). Here are my brief reports about the software I sampled. fallaciously flagged “ought to be” and “may be” as examples of passive voice — a common misunderstanding of the topic. (Passive voice is a backward-facing construction such as “This sentence was written by me”; “I wrote this sentence” is the active alternative. Verb form is not the primary issue.) Worse, there were several real grammatical and syntactical errors in the site’s introductory text (which I used as a test sample for this and the other sites); the grammar-checking tool found none of them.
When I copied and pasted the sample text into’s tool, it showed the same poor results as’s. However, when I clicked on the site’s Advanced Report button, it took me to . . .

Grammarly found nearly fifty errors (or, more accurately, instances of concern), mostly involving what the site terms “writing style,” in the introductory text taken from (The free version did not specifically identify the errors.) When I then plugged in the raw, error-laden version of a copyediting test, it found fewer mistakes than revealed in the text but gave the test text a lower score.

PaperRater found no errors in’s text and only two in the text for the copyediting test — both concerning misuse of hyphens. was stymied by the phrase “not only should the structure of your writing be solid,” reminding me about noun-verb agreement (irrelevant in this case) and by the phrase “your basic default word processor grammar checker,” alerting me that if by using your I meant “you are,” it should read you’re (again, irrelevant).

However, it advised changing you’ll to “you will” and noted that a letter space should both precede and follow an ellipsis and that the first two words in “run on sentences” should be hyphenated — all valid but superficial corrections.

My tests were not rigorous, and I did not purchase any of this software — I merely took a test drive of each company’s freeware trial. However, the only difference I can see between the free and paid versions of these software products is that the paid versions not only flag your errors but also analyze them. The problem is that, whether in simple or advanced mode, these tools missed just about every error that matters in a grammatical review.

These tests confirmed my suspicion that grammar-checking software can at best note only the most elementary errors (and sometimes marks valid constructions as mistakes). Grammar is much too complicated and nuanced to trust to technology. If you want to write well, learn to write well. If you want to have your writing reviewed and evaluated, access the brain of another human being. But don’t even think of relying on software.

Recommended for you: « »

13 Responses to “Grammar-Checking Software Is Soft on Grammar Errors”

  • Oliver Lawrence

    I tried Ginger last year and found that, unless you have a very fast internet connection, it is simply too slow on anything other than short texts.

  • Dean West

    Grammarly is the enemy of the passive sentence. It never fails to rule them erroneous. Sure, we all try to avoid the passive voice, but sometimes a passive sentence is just fine. These grammar checkers do not consider context.

  • Mark Nichol seems to have updated its home page since I checked it and the other sites out. The site’s current text isn’t seriously flawed, but I found some weak spots. I’ll detail them, and provide my revision of the content, in an upcoming post.

  • Dale A. Wood

    Quoted from the above: fallaciously flagged “ought to be” and “may be” as examples of passive voice — a common misunderstanding of the topic.

    Computer programs also do a lousy job of handling the Subjunctive Mood. In fact, I think that this might be the real problem here, since “ought to be” and “may be” are very commonly used in Subjunctive Mood, such as statements contrary to fact, or in wishful thinking, or in statements about the future that might or might not become true.

    1. “You ought to be in prison” (but you are not because the police have not caught you, yet, and even if they did, you got away with it in court.)

    2. “It may be true that descendants of the Norse settlers still live on Greenland.” (There are theories, and some evidence to support them, that some of the Norse people interbred with the Eskimos, and the Norse gradually disappeared that way, as well as by hunger and the harsh climate of the early 1500s.)

    3. “It might be true that there is intelligent life on planets orbiting Alpha Centrauri.” (Nobody knows, nobody knows!)

    I have tested out some rather inexpensive programs from translating from German to English, and vice-versa. Most of these were advertised as being “Revolutionary New Technology”.
    These programs were lousy in many ways, and worth throwing away!

    One of the problems was that they took German sentences in the Subjunctive Mood and always translated them into English in the past tense, Indicative Mood. Also, the Subjunctive Mood is used a lot more in German than it is in Modern English.

  • Ted Cherry

    The site “GINGER” has been omitted. Mark is aware of this site, but did not have the time to include it. I recently downloaded it (free) and found that it works quite well, though not perfect. Some of you may find that it does work for you! The only issue I have with any of these apps is privacy. Email and privacy is probably a thing of the past (if ever) anyway, so I guess it should be of little concern to the majority of us.

  • Cheryl Haium

    Well done, Mark, and well put!
    Human brains may not always agree, but they haven’t yet come up with a grammar-check, or even spell-check, that can replace them.
    Cheryl (Buchanan Burnham) Denk Haium
    P.S. I’ve tried to give you some grief a couple times in the past.
    P.P.S. I’m of an older generation, don’t use social media much and have moved a lot; so, I thought I’d include all of my former last names (even pre-adoption) in case any old friends happen to be hanging around out there! I’ve only been married twice, honest.

  • Greg

    Does this mean I have to learn grammar? But but but…I thought computer programs would do that for me! How can a computer program be wrong?

    Translation is the same. It’s too complicated for current software. I agree with John White, however. Someday…

  • kim jacks

    Have had a chance to check out “StyleWriter” software?
    If so, what are your thoughts on it?

  • John White

    >Grammar is much too complicated and nuanced to trust to technology.

    Famous. Last. Words.

  • Sarah

    Because I am consistently humbled by your daily tips, I do not wish to revel in the irony of a grammar-checking website’s grammar mistakes. I’m simply curious about the errors you found in the introductory text on I believe I found two. Can you share the needed corrections?

    Thank you.

  • Jan Arzooman

    I constantly see Word’s Spellcheck flag the correct use of “your,” suggesting “you are” instead. I’ve finally adjusted it to not flag incomplete sentences—I edit fiction a lot and there are going to be incomplete sentences. I’ve always used Spellcheck’s spelling and grammar check as a first-round and almost last-round spin-through of a document. It does flag quite a bit, but, as pointed out, a person needs to know the limitations.

    I think I’m a little surprised that software hasn’t gotten better, but, hey, it’s job security for editors! Thanks for the review.

  • Charles Ray

    This is also true of Spellcheck on the Word processing programs. Mine, Microsoft Word 2010, for instance, consistently flags ‘its’ and ‘it’s’ incorrectly, and can’t seem to tell when I’m using the contraction for ‘it is’ This is but one example of the grammar checking function flagging aa wrong a phrase, word, or sentence that is correct. The best grammar checker in the end, as you rightly point out, is the ‘wetware’ of your brain.

  • Jeanette Flint-Zalfini

    I already am a subscriber, but I didn’t get the free Basic English Grammar book. I didn’t want to subscribe again to get it. Should I? Can you send me a link to the download? Thanks!

Leave a comment: